Sound record for talking machines



April 1s, 192s.

. w/r'NEss -1 r foR/vsrs 1,530,567 J. w. OWEN -T AL .SOUND RECORD Fon ,TALKING ncl-:INES

' Filed Feb. 14, 1921 s sheets-shut 1 n r'l I3 1926.. 1,580 567 A!! J. w. owEi EVAL SOUND RECORD FOR TLKING MACHINES. f

Filed Feb. 14, 1921y 5 sheets-sheet 2 f I @y l Error/vers 1,580,567l J. w. .OWEN r-:r Al.

SOUND RECORD FOR TALKING MACHINES Filed Feb. 14, i'1921 s sheets-sheet s .April 13,1926. l

/NVEN TORS WITNESS Patented Apr. 13, 1926.

UNITED STAT-Es PATENT oFFlcE.

`JAMES W. OWEN', 01? CLAYTON, AND ALBERTIS HEWITT, OF CAMDEN, NEW JERSEY, ASSIGNOBS T VICTOR TALKING MACHINE COMPANY, A CORPORATION OF NEW JERSEY.

l.souND- RECORD ron TALKING MACHINES.

- Application med February 14, 1921. serial No. 444,796.v

To all wlwm it may concern:

' Be it known that we, JAMES W. OWEN and ALBERTIS HEwrrr,' "both citizens of the United States, and residents-'of Clayton, in

l the county of Gloucester, and Camden, in the count of Camden, respectively, and the State of ew Jersey, have invented certain new and useful Improvements in Sound Records for Talking Machines, of which the l0 following is a full, complete, and exact disclosure, the subject-matter of this invention having been also disclosed in our prior appliv cation N o. 877,803, filed December 17, '1914,

, of which the present application is a 'oontinuation in part. v

'lhe present invention relates to sound record tablets used in connection with sound reproducing machines or talking machines, and particularly relates to the sound record groove therein provided with undulations corresponding to sound vibrations. Y Inasmuch as the record and record groove may be produced in a variety of ways differing, however, from the manner in which sound records have previously 'been made, the relation which exists between the processes by the practice of which the present invention is made and those by 'which soundl record tablets have heretofore been commonlymade will be clearly set forth.

YWhen a sound record tablet is cut or engraved in a -wax tablet in a well known manner, the sound record groove may vary slightly in width when measured at right angles t'o the general direction of the groove,

'and while this peculiarity or characteristicv may not be a serious objection, and may not interfere with the reproduction of 'sound from certain records, it is nevertheless de- 0 sirable, in some instances, to eliminate this peculiarity.` -A cutting stylus, when vibrating rapidly and wldely in a direction transverse to the general direction of the groove being formed thereby, may producev a groove which is narrower in certain portions thereof than in others, such narrowv portions being where the vibrations are frequent and of relatively great amplitude.

AIn reproducing sound from a tablet having l a groove of such variable width, la reproducing sty-lus might tend to janitor wedge in the narrow portions of the groove and `coi'xeequently tend to rise up from the bottomof the groove in such narrow portions and ride upon the side walls of the groove. Such an .action of the reproducing stylus might tend to unduly wear or scratch the groove and injure the record of sound at such points. One of the objects of the pres-l ent invention is to provide a record of sound, the groovev of which does not have the peculiarities above referred to. i

The quality of the sound which may be.

produced from a sound record tablet may vary with the shape of the groove in cross section and with thedepth of the groove.

Inasmuch as sound record tablets 'are'made in widely different parts of the world by diterent individuals on different recording machines equipped with different cutting or engraving styll, the grooves of record tabletsthat present in a given record. The present invention 'has for one of its objectsfthe production of a. record having a groove therein of the best form, `shape or depth for reproduction lof sound therefrom, such record being produced or made from a sound record tablet having a groove of different shape or proportion.

Another object ofthis invention is to make a record in which the sound record groove is of a. standard sha land size, so that wha-tever may be the epth, shape or form of the groove originally recorded, the commercialv record grooves may have substantially the same shape in cross section, the same depth and thesame width transverse to the median line of the groove at every point throughout the len h of the grooves.-

When commercie 'sound records, produced under thel widely varying conditions above indicated, are placed upona reproducing machine to reproduce sound therefrom, a reproducing i needle or stylus 'of substantially xed or standard size may or may not tit perfectly within the' groove of such record. When the stylus does not properly lit the groove, its action is first that of being ground and Shaped by the abrasive action of the record until it conforms to the. shape 5 of the groove. This failure of a stylus to fit the groove tends to injure the walls of the sound 'record groove, especially when the stylus is hard and Wear resisting. A further object of this invention is to produce a record in which the sound record groove 'is standardized so that a standard commercial reproducing stylus will perfectly lit the sounda record groove.

The volume of sound reproducible from a Sound record may also vary somewhat with the form and shape of the sound record groove. Uur invention relates to the production of a record in which the sound record groove is diderent from that formed inthe recording thereof, so that the record which gives too loud a reproduction may be made to give a softer one, or a record which gives too thin or soft a reproduction, may be changed-by varying the walls of the M5 groove so as to be capable of reproducing sound with greater volume, all without detracting from the quality of the tones reproduced in othervrespects.

A. further object of our invention is to a@ produce a metallic sound record tablet, the walls of the groove of whichare wrought and highly burnished, and polished in order that a commercial record produced therefrom shall have equally smooth burnished walls to reduce the abrasive action and scratch between the stylus and the walls ofl the groove. A commercial record so made with highly burnished or polished walls may be operated a greater number of times without injury to the record tablet than one in which the groove is not so burnished. An object of 'the invention is therefore to produce a commercial tablet from which sound may be reproduced a greater number of times than it can from an ordinary tablet Without substantial injury to the walls of the groove.

@their objects of our invention will appear in the specification and claims below.

Referring now to the drawings forming a part of this specification, Figure l is a greatly enlarged diagrammatic plan view of a sound record groove having undulations corresponding to sound waves' in the side walls thereof. full lines is indicated such a might be formed by' a cutting tool in was or other suitable tablet whe stylus is vibrated rapidly uder the in- ;'fiuee of sound waves ci relatively great iitude, while dotted lines is indicate l rammatic manner the e to which the cut sound i .fe may lie an other portions as the ed i g stylus vihr-atesl intatti' Figure 2 is a view on the same enlarged scale as Figure l of a sound record groove such as may be produced from the sound record groove shown in Fig. l and which is formed in a tablet embodying our invention. The sound record groove of Figure -duplicate of the record shown in Fig. 3, but

stiifened by a metallic backing.

Figure 5 is a diagrammatic. showing indicating the manner in which the groove of Figs. 3 and 4 is widened in itsnarrow porftion by the passage therethrough of a spinning stylus ora metal spinning tool of hard umvearing material.

Figure 6 shows a metallic record similar to that shown inA Fig. 4, but in which the groove is a duplicate of a groove in a sound record tablet which is too deep and the side Walls are too nearly parallel to give a good reproduction of sound and Figs. 7 and 8x indicate the manner in which such a groove is wrought into one of standard size and sha e. p

Figure 9 is 'a diagrammatic view of another metallic recordsimilar to that shown in Figures 4 and 6, but in which the sound record groove as originally recorded is too shallow and the side `walls thereof make too great an angle with each other and Figure 10 shows how that metal record is hrst lapped and prepared for the travel or traverse therethrough of a spinning stylus to produce therefrom a groove of standard shape and size such as is indicated in Fig-- ures 5 and 8. Y c

Figures ll, 12 and 13 indicate diagrammatically another method whereby the soundv record groove in avmetallic tablet and which is too shallow and narrow to be used from which to produce duplicate commercial ,records capable of being reproduced on ordinary talking machinesrnay be changed by spinning out the groove to one of standard size and shape. The sound record groove in'tliis instance may be a groove originally formed in any desired manner and just dee) enough to guide the spinning stylus an( cause it to follow the undulations corresponding to sound waves in the walls thereof during the forming or spinning or expanding of the standard ,sized groove therein.

Figure i4 is a pian vieu' of one forni of apparatus for spinning out the walls of a metallic sound record 'to change the groove ist therein from` an undesirable groove lfor spinning stylusL such'as may be employed 1n formlngour new and improved record.'v

Figures 17 and 19 show ma more orless diagrammatic manner, an apparatus which is used for brushingxpolishing and burnishing the "face oT a metallic sound record and the side and bottom` walls" of the sound record 'groove therein, andv for lapping or grinding away the fiat surface of the-face of a metall record when that' step is desired or required, and for rounding the edges of the sound record groove to cause themto gradually merge into the top plane surface of the record. In Figure 17 the metallic record is shown as being. lapped, polished and burnished by a brush carrying a suitable abra' sive pressed against the surfaceof the metallic record.

A Figure 18 indicates on a greatly enlarged f scale, and in a greatly exaggerated manner how, in brushing, burnishlng or polishing A `the face of the sound record',the inactive walls of the groove may be that portion `of the groove which is most greatly affected or modified thereby.

Figure 19 is a diagrammatic ind1cation ,of the way in which the edges ofthe groove are rounded to remove thesharp4 corners between the side walls of the sound record groove and the top surface of the record tablet.

F igure'2() indicates the -way in which the operation indicated in Figure 19 rounds oll the corners of the sound record groove in a metallic record; and V Figure 21 is a fragmentary greatly -enlarged cross-sectional View of a fragment of a commercial record embodying this invention and formed from the metallic records above described in any desired .well known method of duplicating metallic records, as -for instance by the electroplating process of making a die or pressing matrix from said metallic 'master records having a spun groove therein and pressing plastic material with such a die to produce commercial records.

It is to be understood that in any of the figures the showing is diagramma-tic and exaggerated, in order to clearly illustrate what isbeing done and how the groove, comprised .in the invention hereof, is'produccd. The fragments of sound record tablets shown in Figures 3 to '13 and 20and 21 are shown on an exaggerated and x'n'agnified'v scale,/and the relative proportions are .not necessarily exact.

In Figure 1 is representedl a cutting orl engraving tooll and a groove 2 cut in a suitable wax' tablet thereby,` the cutting tool being vibrated transve-rsel to the direction that the tablet moves un' erthe same tool. The cutting tool 1 is attached to the stylus of a reproducing sound box (not shown) to yproduce a laterally undulatory oove of even depth, the side wallsof whicrare provided with undulations correspondin to sound waves. This groove 2 formed y a cutting stylus is indicated in the wavy double line (in full lines) the extreme movement and direction of the cutting stylus ;1 being indicated by the double' headed arrow 3.

When the plane oty the cutting edge of tlie A. -st lus or tool 1, vibrated under the muen ve o soundwaves, extends substantially transverse tothe direction of the'movement df the tablet-thereunder, the groove 2 formed in theface vof the tablet will be of'constant width when measured parallel to the plane of the cutting edge of the stylus; i. e., parallel'to the arrow 3, but the groove will be va'riable in width when measured at right angles to the median vline 4 thereof. Of course, inactual practice, these variations in the width of the groove 2 are relatively small, but there may be relatively narrow or constricted portions 5,- particularly where vthe vibrations are frequent and the amplit'ude great. It must be borne in mind, however, that the showing in Figures 1 and 2 is diagrammatic and exaggerated for the ur` pose of vclearly illustratmg these peculiarities which are more or less common to soundrecords formed by a cutting stylus.

After such a groove as is indicated in full line'in Figure 1 has been formed in wax or other suitable material and constituting the master sound record tablet, and a metal record has been formed therefrom, thatgroove in said metal record may be wrought, altered,chan ed, or spun into a 'groove 6 in which the wi th is uniform when measured at right angles to the median line 4 thereof. Theh relation which such a changed or altered sound record groove 6 (shown in Figure 2) bears to the Y original sound record oove (shown in Figure 1) is indicated by the dotted lines in Figure 1. It is the purpose of this invention to produce a sound record, the groove of which is changed from such al one -as is illustrated in' `Figure l'into a groove When altered or Wrought or spun into the form illustrated in Figure 2, but the volume "three consecutive convolutions of the sound record groove 2, the middle of .the three oonvolutions being shown as sectioned at one of the narrow .portions 5 of the grooveshown in Figure 1. The cross-sectional Width, depth and shape ofthe sound record groove at its widest points may be assumed in this instance to be correct and as not requiring change or modification, thus making the o-nly'thing to be doneto the grooves of this particular record to be that of changing the narrow portions of the groove into the same size and shape of the Widest portion thereof When measured at right angles to the median line ofthe groove. f

After the Wax master 7 of Figure 3 has been formed in any approved manner, as by a vibrating cutting or engraving tool, the first step of the process by the practice of which our record may be made, is to form a metal record l0, the groove 2 of which is a duplicate in every respect of the sound record groove 2 in the Wax master record 7. This metal duplicatemay be made in anyv suitable manner as for instance by an electroplating process and is shown in Figure 4 as consisting of a shell 8 formed by an electroplating process and having a sound record groove 2 therein like the groove 2 in the Wax master record tablet, and preferably backed by a stiff plate o-r disc of metal 9 in order tol give rigidity to the same. The shell 8 and metal backing 9 together form a metal record 10.

After the metalrecord l0 has been formed, it may be desirable to subject thesame to a brushing or polishing process to biirnish the side and bottom Walls of the sound record groove therein and to remove any slight irregularities' in the Walls thereof which might produce a scratch during the reproduction of sound therefrom. This polishing on paratus illustrated in Fi re 17, in Which a face plate 39 mounted o the end of a shaft 40 suitably journaled in the bearing 4l is arranged to be rotated at any desired speed by any suitable driving mechanism no-t shown. From the front of said fac-e plate 39, a 'spindle 42 pro-jects far enough to permitof the fitting thereover of a .Washer 43, a exible metal plate 44 and the metal brushing step may be pprmed on the apface of the metal record l0 With the result that thebrush enters into the grooves of the face'of the metal record and the. side and bottom Walls of said grooves art smoothed, burnished and polished, and any imperfections or irregularities therein which are not removable by the spinning process, to be later described, are eliminated. The shaft 40, during this process is revolved preferably in the reverse direction to that in which the record Would be revolved in reproducingl sound therefrom.A The brush 47 i With the polish-ing material therein, enters into the grooveand highly polishes the sid and bottom Walls of the groove.

After having been brushed as aforesaid With electroshine, Which has a slightly abrasive action` upon the face of the metal record, the record may then be subjected 'to a'further brushing step, a soft brush in this step being preferably impregnated with a much finer polishing material, such as gold rouge, and pressed against the face` of the metal record to impart to the surface of the record and to the side and bottom Walls of the groove therein a very high and smooth polish.

There is another result which is effected during this burnishing process justpdescribed and which is quite important. The revolving of the metal record 10 during this brushing process in the opposite direction to that in which it would be revolved to reproduce sound therefrom subjects that Wall of the groove or part of the vWall of the groove f which is inactive during the reproduction of sound from the record to av greater Wear or abrasive action than the active portion of the Wall is subjected. In Figure 18 is illustrateddiagrammatically a sound record groove 2 provided With` a few undulations. Now if during the reproduction of sound from a record containing that groove 2 the movement of the groove with respect to the reproducing stylus is in the direction of the arrow ,58, tlienthose parts 5.9 of the walls of the sound record groove 2 are the parts which are active inV actuating lthe stylus during the reproduction of sound from ythose particular undulations. If then the metal record 10 be rotated 'in the reverse direction during the polishing process above described, that is to say, in the modified by the polishing process for thebrunt of the polishing will. fall upon the4 inactive walls of the sound record groove,v

and if that portion of the groove be narrow or constrictedas fully explained above, then the action of the burnishing brush on the groove will be that of tending to widen or' enlarge the groove at the constrictedor narrow portions thereof without injuriously affecting the active lwall and consequently without injuriously affecting the sound reproducible from the sound record groove.

To vchange the groove of' the metal record 10 from one of varying to one of uniform width, this vmetal record 10 is subjectedto the action of a hard substantially unwearing stylus which is held with considerable pressure in the groove and is caused to slowly track throughout the length of the sound record groove. One apparatus for performing this operation is shown in Figures 14 and 15 in which a spindle 13 is journaled in a suitable base or standard' 14, the top of which is provided with a circular turn table 15 'upon which the metal record 10 may be mounted. Upon the top of the base or support 111 is abracket 16 provided with f two alined conical bearings' 17 and 18.

Between thesbearing points A17 and 18 is a still or rigid support 21, rotatable uponI the bearing points 17 and 18 as centers. Extending outwardly from the-support 21 is an adjustable clamp 22 provided with a socket 23 within which one end of a resilient spring rod 24 is securely held by a set screw 25. The clamp 22 may-be rigidly secured at any point on the support 21 by a lset screw 26. The outer end of the resilient spring rod 24 is provided with a transverse hole or opening to receive the upper-'end 28 of the stylus`27 secured therein by a set screw 24.

The spinning stylus 27 preferably7 con.

Sists of 'a cylindrical shank 28, preferably of steel, a stylus tip 29, preferably a jewel, such as a sapphire or diamond, and a coupling 30 for rmly uniting said tip and said shank.

The lower end of'the stylus tip 29 'is referably conical in shape, terminating at its lower end in a rounded point shape-dto exactly tit. int-o a properly formed standard sound record groove. l

The spinning apparatus for re-shaping, changing, altering, working upon, burnishing andpolishingthe sound record groove is operated as follows. The rod 24 isnor- Inally horizontal or mounted to swing in operator and swung over toward the center of the turntable so that the tip 29 will rest in the outer end of the spiral groove. The pressure with which the stylus bears upon the metal record 10 will depend upon the stiffness of the rod 24 and lthe position to .which the clamp 22 has been previously adjusted on the still support 21. Before the tip 29 is actuallyplaced in the spiral groove of the metal record, the surface of the metal' record is given a thinA coating o lubricant, sue-h as lard oil. with which the tip29 engages the metal record during the operation of the device is dependent upon the kind of a change which is to be Ina-de in the sound record groove, hatl the 'tension of the rod 24 is always so adjusted as tocause the tip to bear with considerable pressure against the surface ofthe metal record.

After the tip 29 has been placed in the outer end of a sound record groove nearest the periphery of the tablet, the turntable and record carried thereby are slowlyy revolved in a clockwise direction, preferably at a speed of frein two to five turns per minute, and when' so operated .the stylus tip 29 will traverse the groove in the same directionthat a reproducing stylus would traverse a groove during the reproduction of sound from, said' record. i

As the turntable 15 and metal record. carrier thereby are thus slowly revolved, the tip 29 ofthe stylus will exactly track or follow in the groove of 4the metal record 10 until it has traversed the entire len h of the soundy record groove and in so dolng it will faithfully `follow all the minute un dulations inthe sides of the sound record groove. The jewel tip 29, however, will spin or spread out or stretch the metal forming the walls of the sound record groove in those places where the groove is narrower or of a diii'erent size or shape from that of the tip of the stylus itself and make The pressure all of the'parts of the groove 6 so'formed The angle which the stylus 27 makes with llO the plane of the top surface of the metal record 10 is preferably just as near 90 as possible, because the nearer perpendicular to the surface of the record the stylus is, the more uniform in transverse cross-section will the groove 6 ultimately be. It has been found, however, that when the stylus makes an angle of exactly 90 with the metal re cord, the stylus itself is liable to vibrate or chatter. 'lt`is preferable therefore to give the stylus during the,` spinning operation a slightly backward rake and good results are obtained when the stylus is set at 'an angle of from 80 to 88 to the plane of the top surface of the metal record..\

In this way we produce our new and improved sound record tablet in metal and 'change aA metal record from one having a ysound record` groove which is variable in width when measured at right angles to the median line thereof to one in which the sound record groove is uniform and standard in shape, size and width and in which the groove is of unvariable Width throughout its length when measured at right angles to the median line therof. The groove in the metal record is thus changed from one substantially like the groove 2 of Figure l into one substantially like the groove 6 in Figure 2.

Referring now back to Figure 5, the tip 29 of the spinning stylus is shown as having traversed'that convolution. to the right of the said stylus and since the. cross-sectional shape of the groove at that particular point was originally the same as that of the tip of the stylus, substantially no change was produced therein by the spinning stylus 29.-

The tip is shown as being' in the intermediate convolution which in Figures 3 and l is shown to be one of the narrower portions 5 of the groove. In traversing this narrow or constricted portion, the stylus has spun out slightly the metal of the walls of the groove and is shown as making it exactly like that convolution through which the stylus has passed and like the one to 'the left of the position shown and through which the stylus will next pass.

But this invention is notte be construed as limited to a record in which portions only of the sound record groove have been changed, altered, wrought upon or spun. The shape and size of the groove originally recorded in a master record may be altered in other respects and throughout the length thereof as will now be described.

It may happen that the original sound record groove was not correctly made. "it may not be of the desired shape or size throughout its length. Some records may be provided with grooves the side walls of which are too nearly straight or are too widely diverging to produce the best reproduction of sound therefrom. Some grooves may be too deep and others too shallow. Our invention has for its purpose the production of a record first in metal with a groove exactly like the undesirable groove and then changing the groove in that metal record to 4one of the desired shape, form and size by mechanically acting upon the side Walls and bottom of the groove by' a metal working process. Our invention also embodies the commercial record tablet, a duplicate of said altered metal record adapt ed lfor usev on a suitable sound reproducing machinev and wherein the sound record groove is an exact duplicate of the altered groove in the metal record. The commercial record above referred to may be formed in any suitable manner from the altered metal record, as for instance, by producing a matrix of the altered metal record by an electroplating process, and backing up the shell so formed to make a die from which commercial records may be pressedV in a suitable plastic record material.

Referring now to Figures 6 to 8, it still being borne in mind that the drawings on a greatly enlarged and exaggerated scale, Figure 6 shows a' crossesectional view of a fragment of a metal record similar to that shown in Figure 5 but in which the shell contains a duplicate of a sound record groove which is too deep and the walls of which are too narrow or too nearly perpendicular. This metal record is designated as 34 and the metal shell 35 provided with the too deep and too narrow groove SQ'and further with a rigid still metallic backing 36. For the purpose of illustration, it is assumed that the groove 32 is too deep by the distance between the top surface of the record tablet and the dot and dash line 33 and that the angle that the side walls Should make with each other is that of the tip 29 ofthe stylus, the contour of which is also shown infdot and dash line in Figure G. This groove 3Q- in this metal record 3lmay also be readily changed into a record having a groove 6 of Fig. 2) of correct and desired size, form and depth.

The face of the metal record 34C is lapped or ground down or polished away until the groove therein is of the proper or correct depth. and iu the particular instance illus tratcd in Figure 6, the material of Fthe face of the record should be abr'aded down to the dot and dash line 33.

The lapping or grinding down of the face of the roet-al record 34@ to produce a lgroove 38 of the correct depth may be performed on the same apparatus as that used for the brushing or polishing step above described and as illustrated in Figure 1'?A except that instead of the brush 47 a yielding, substalr tially flat fabric pad impregnated with a metal record 34 While the shaft 40 is rotated* andthe pad is slowly Worked back and forth until the face of the metal record is lapped or ground and polished down to leave a sound recordgroove 38 of the proper depth..

During this lapping operation, thel metal record is preferably rotated so as to turn the record in the opposite direction in which a commercial sound record tablet, similar to the metal record 34, Would be rotated to 'reproduce sound therefrom.

After the lapping step above `described,v

the face of the metal record 334 is brushed with a soft brush impregnated with electrogroove.

l After the metal record Sebas-been changed' in the manner above indicated into a'metal 7, the stylus being assumed to have traversed the convolution to .the right thereof and to have not traversed the groove 38 to the left thereof. It isfof course understood vthat before the stylus 29 is caused' to traverse the groove in the face of the metal'record 37, the surface ofthe record shall first have been lubricated as abovedescribed.

In Figures 9 and 10 is similarly diagram-v matically shown a' groove which is too shallow and too Wide and the side walls of which form too great an` angle with each other for the best reproduction of sound therefrom. Figure 9 is a metal record isi'milar `to the metal records 10 and'36 and is assumed to f. steps above described with the result that the metal record 55 having the groove 56 vin the face thereof, will' be produced (see Fig. :ure 10). l

the metal spinning machine shown` inl Figg The record 55 is then 'paced upon Vmachine. shine and gasoline and afterwards with a` soft brush impregnated with gold lrouge to produce a very high polish on the facey ofy `the record and the Walls ofv the record ninglstylus 27 through the groove of the ure 15 and the groove 56 is spun by the spinning tool out into the correct or standard or predetermined size and shape in the same manner as has been above described to pro` *duceV a metal record vhaving a spun groove therein like that shown in Figures 2, 5 and 8 above described.

In Figures 11, 12 and 13 arel illustrated afurther modification of the process by means n of whichtheinvention of the record herein 75 claimed may be produced.

'In Figure 1l is shown a metal record 11 having a sound record groove 12'Which is too lsmall and too shallow to actuate a stylus of a commercial sound reproducing .0

This groove 12l may have been produced inI any desired manner to have undulations in the side walls corresponding to sound vibrations. 'Inasmuch asl the` spinning step is carried out at a relatively u l .slow speed such a light. or shallow roovel aslthat indicated in Figure 11 is su cient to guide a spinning stylus and cause it to track throughout the length of the groove and spin out the groove in the manner herel tofore described. A

-n'carryi'ng out this spinning step it is, sometimes desirable to first give VAthe surface of the metal record a thin skin or platn ing of metal. In Figure 12 the metal record 95, 11 isshown as provided with a very thin layer 19of nickel but it is to ,be understood that in these figures the thickness of the nickel deposit is greatly' exaggerated for the sake of clearness. c l

After the metal recordfshovvn in Figure 12 has been made', it isy vthen placedupon the turntable 15 of the spinning apparatus andV the spinning stylus 29 is caused to track through the groove, spinning out the vgroove ,105 tothe size, depth and shape requiredv and producing ar spun groove 6 therein, in the manner previously described in connection .with the spinning of other metallic records.,

It will, of course, be understood that the y faces of' all the metal records which are above described as having been subjected to the action .ofthe spinning stylusto expand or stretch or Work the Walls of the groove into a new and diii'erentshape must H5 of course. beof a ductile metal, such vas cop- 'jper andthe body 11of the metal record `shown in Figures 11, 12 and 13 must be-of copper or somel other ductile material which will yield under the action `of the spinning tool and conform to the shape imposedrupon itfby the action of the spinning` tool, and that before the spinning tool is caused 'to track thi ough the grooves of any 'of the 12 metallic records acted thereon, it is prefo erabe to give the face of the metal record a thin coat of a suitable lubricant.

If by reason' of the passage of the spinmetal record, ,the displaced metal should 130 rise above the plane of the surface of the metal record, the surface of the metal record may thereafter again be lapped sufficiently to remove thesame and to produce a polished or burnished surface. It is to be observed that after the metal records 10, 37, 55 and 11 shovm in Figures 4, 7, 10 and ll have been formed and the grooves thereof spun., the lresulting metal records (Figure 5) will be all substantially alike and they will al have the type of spun groove illustrated in Figure 9.. lVhatever, therefore,

maybe the structural characteristic of the.

groove in the original or master record and in the metal record first produced therefrom, the groove in the final metal record may readily beinade int-o a standardized groove ,of uniform shape, depth and Width in crosssection and of uniform width throughout the length when measured at right angles to the median line thereof, and this final standardized metal record may be thereafter retained as a metal master record from which pressing matrices may be made in any of the well known methods of making such pressing matrices. The sound record groove of a. commercial record 71 pressed from such a. matrix 'will be identical in its shape, size and form with .the groove 6 of the metal record 10 and will be of uniform Width when measured at right angles to the median'line thereof. rthe Walls of the groove in a commercial record 71 will be duplicates of the wrought, spun, stretched, expanded,

metal Walls vof the metal record.

rlhe action of the spinning ystylus inA traversin@ the groove of the metal records is to slightly spin or displace the metal of the walls of the groove. rllhe spinning also tends to burnish and polish the Walls of the groove. But lthe brushing and burnishing of tlie-\\'alls of the groove is best effected b v the apparatus shown in Fig. 17 and it tends to remove from the Wallsvof the groove those minute scratches and dull places which are apt to occur in the grooves of sound record tablets, and the smooth Wall so pro-L` duced tend to greatly reduce the friction between the reproducing stylus and the walls of the groove. having such smooth grooves have a longer life than ordinary Sound record tablets made by other processes.

lin explaining the relation of the metal record involving this invention with respect to records having grooves of a shape other than that shown in Fig. 2, the metal record 10 (Fig. d) was referred to as being :i duplicate of a Wax master, such as is shown in Fig. 3. But it is to be understood that such metal record as is shown iii Figs. 4, 6, 9 and even Fig. 1,1 may be obtained by any Well known process from any kind ofy a record, thus the metal record 10 4might Sound record tablets be made from another metal record having a groove like that shown in the record 10, or it might be made from a die or matrix as distinguished from a metal record such as has been above described. Therefore in its broader aspect, the record shown in Fig. 3 may be more properly termed a primary record tablet Whether it be a vfax master or some other form of record tablet, or a matrix.

The tip of the spinning stylus may, of course, be of any desired shape suitable for spinning purposes, but it is preferably subst antially paraboloidal. This does not mean that its generating curve is necessarily a true parabola, for -in some cases. if desired, the generatrix might be an ellipse, or an arc of a circle. The depth of a sound record groove is exceedingly minute Within the distance bound by the Walls of the sound record groove, and Within those limits the curve of the parabola or an ellipse or of a circle may so closely approach each other as to make it rather diiicult to distinguish between them. When, therefore, for brevity', the shape of the tip is referred to herein as paraboloidhl, it is intendedto cover and include that shape which resembles or approximates that of a paraboloid, Whether the'generatrix be a true parabola, a true ellipseya circle or a straight line making an angle to the axis of the stylus and provided Witha smooth curve Where the generatrix meetsthe axis.

lt is to be noted that in treating the metal record by subjecting it to the lapping or grinding steps above referred to, the use of the pad with the abrasive material thereon may tend to slightly Wear' away,

remove or round 0E any sharp corners` Whichniay exist at the intersection of the side Walls of the sound record groove `with the plane face ofthe metal recoidabut in any instance Where sharp corners there exist to a marked degree, it has been found de. sirable to employ a separate step to positively effect the rounding off of the sharp corners where the walls of the sound record groove meet. the Iplane surface of the face ofthe 'record A As the preferred means for accomplishing this end, the metal record is sub1ected tothe action of a soft or yielding pad 70, having a rounded or substantiallyspherical surface for engagement With the face of the metal record. 'lhis pad 7 (1 (Fig. 19) is impregnated with any suitable abrasive material, such as electroshine, and Vis Worked back and forth, manually, across the face of the metalireeord While the record is being rotated on the apparatus indicated in Figs. 17 and 19. 'lhe action of this rounded pad in removing the sharp corners, is more ef` esv surface of this Asoft pad or ball 70 permits the same to accommodate itself to the surface of the record and Ato enter, to a certain extent, the innerl side walls ofthe groove and to bear upon and wear away the sharp corners.

The removal of thesharp. corners by the step just described may be effected at any suitable time, but it preferably follows any burnishing ofthe groove with the brush and any lapping of the face of the metal record, if lapping is necessary, 'and prior to any spinning of 'the groove by the hard stylus. The removal of the sharp corners or edges from the metal record will remove any sharp corners ila-the pressing matrix subsequently made therefrom 'and between the face of the.,matrix and the side Walls of the sound ridge thereof and therefore the i commercial record pressed from such matrix will lalso be free from any sharp cornersl or edges Where the Walls of the sound record groove meet thje surface of the record. The rounding or removal of the corners or edges, tends to lengthen the life of the commercial record tablet, because as' the reproducing needle wears, during the reproduction'otl sound from a record, the surface Where the walls 'of the sound record groove curve o-ver and merge into the plane surface of the lsound record tablet does not come into engagement with the reproducing. needle and hence does no t produce shoulders on the stylus which roughen and break down' the walls of the groove therein.

For the purposeof illustratingthis step l of removing the sharp corners, Fig. 19 shows is shown as applied to the metal record 10. (Fig. 4) prior to the passage of the spinning a'metal record being revolved and the surface of it being subjected to the soft pad 7 0. In Fig. 20, the rounding over of the corners stylus therethrough, but lit should be remembered that the drawings are rather diagrammatic as distinguished from being exact in size, form and proportion and that a number of spinning and. lapping operations may be requiredto bring a groove not of standard size or shape into a groove of what we have termed stand-ard size and shape and that this rounding of the corners is preferably per 'formed prior tothe last lapping operation when the effect of the last spinning operation lmay be relativelyl slight, too small to accurately illustrate in these drawings. It is to be understood, however, that the last spinning operation will not destroy the rounding of the corners of the sound record groove preferably effected immediately prior to .the last traverse of the spinning stylus through the groove of the metal record.

In this connection, it is to be understood that the corners ofanymetallic sound record groove may-be similarly rounded when desired to keep the surface Where thel sound record groove merges into the top surface of the record away from the abrasive action of the stylus thereon, or conversely to vkeep the stylus away from the abrasive action of the record. at this point in the commercial duplicates made therefrom and that 'the step of removing the sharp corners may be introduced or omitted in any particular case as occasion might require.

Having thus described our invention, what we claim and desire to protect by Letters Patent of the United States is 1. A sound record tablet having in the surface thereof a spiralv groove provided with undulations inthe walls thereof corresponding to sound waves, said grooves having rounded corneis at the points where the `Walls of said groove merge into the unrecorded portion of said tablet.

2. 'A sound record tablet having a groove in the face thereof provided with undulations corresponding to sound waves in the side Walls thereof,sa1d groove belng of uniform width transverse to the median line of'` said groove and having rounded corners at the points Where the side Walls of the groove merge into the unrecorded portion of the sur ace of said record.

3.aA metallic sound record having a laterally undulatory spun groove.

45, A metallic sound record having a laterally undulatory spun groove of substantially unlform depth and curved surfaces joining the Walls of said groove to the surface of said record. i 5. A sound record having a laterally undulatory spun groove vof substantially uniform depth and of uniform width throughout the length thereof when measured trans-` verse to the median line of said groove.

6.' A record tablet having a sound record 'groove with undulations corresponding to ured at right angles to the median line thereof.

9. A record having a spun sinuous sound record groove of even depth' wlth undulations corresponding to`sound. waves in the lwalls thereof, the surfaces of said side walls being mechanically stretched apart to form a groove of constant width measured at llO being of even depth and thel walls of said vgroove being Spun to an even 'width measright angles to the median line of said being spunto an even Width throughout the groove. length thereof.

l0. A sound record having a. lateraly un- V In Witness whereof, We have hereunto set 10 dulaory spun groove. our hands this 12th day of February, A. D.

11. .A record tablet having a sound eoord 1921.

groove with unduletions corresponding to JAMES W. OWEN. sound Waves in the Walls thereof, said groove ALBERTIS HEWETT. 

